Nacreous graphite pigment



2,s1s,o1 NACREOUS GRAPHITE PIGMENT.

Lawrence Suchow, New YorkQN. Y., assignor to Francis Earle Laboratories, Inc.,. Peekskill, N. Y., a corporation ofNewYork it I. a

No Drawing. Application February 7, 1957 Serial No. 638,685

8Claims. (Cl. 106-148) many transparent or translucent substances by incorpora tion ofthe nacreous material within the substance itself.

.For example, simulated mother-of-pearl knife handles and fountain pen barrels can be made by incorporating a nacreous pigment in a plastic, such as celluloseacetate,

which is then molded into theappropriate shape 3 Simulated pearl buttons are made from discs which are cut from acrylic or polyester sheets containing oriented pearly jpigmentrthe nacreous pigment is suspended in theappropriate polymerizable resin, which is then cast to form a solid sheet in which the nacreous effect is incorporated. It is important in this application that the plate-like crystals have the proper orientation at the time of gelation. t

To produce pearly luster in surface coatings, nacreous pigments are suspended in a light-transmitting, filmforming vehicle whichis applied to a surface so that the thin, plate-like crystals of the pigment lie parallel to one another and generally perpendicular to incident light. The nacre is caused by simultaneous reflection of light from the many parallel surfaces at different depths,

which produces a velvety pearl-like luster rather thanthe.

metallic mirror-like luster characteristic of light reflected from a single surface.

Pearl essence, which is a guanine composition derived from fish, and lead hydrogen phosphate are examples of effective nacreous pigments. o

A nacreous or pseudo-nacreous effect is also obtained when the pigment consists of opaque, plate-like particles. In this case, the effect is due entirely to reflection from the top layer of particles, and the three dimensional effect obtained is due to variation in the height of the top layer of pigment particles in o the film, coating or plastic. Aluminum flake is an example of this type of' pigment.

The pigments of the present invention also fall within this category.

In pigments of this type, it becomes a problem to produce lustrous color effects which have high heat stability. Such effects are not generally attainable through the use of dyes which are further limited as to the shade or tone of a given color which may be produced.

Moreover, it has heretofore not been possible through the use of dyes to produce a pure black, lustrous nacreous effect.

Accordingly, it is an object of the present invention to provide a novel composition which will produce a black lustrous nacre.

in diameter, with from powdered as a wetting agent.

it diluted in ethylene glycol content of from 10to 20 percent.

with respect to each other, and

2,875,076 latent ed F eb.;24 1?5 9 Another object is to provide a method for economicallyjand etliciently preparing such a composition.

A further object ofthisinvention is "to provide novel articles of manufacture in which are incorporated nacreous graphite pigments. z a

These and other objects .of this invention will become apparent from the following description:

It has'been found that nacreous pigments of finely divided graphite particles produce an excellent pure black nacre with very good lustre. Such pigments are further found to have high heat stability and are prepared by grinding graphite to the desired fineness in a liquid vehicle. i

The nacreous graphite may be prepared by milling graphite to a desired particle size and, configuration hereinafter disclosed. f a

. In a second method, plate-like crystals of nacreous graphite are prepared by milling graphitesuspended in a carrier such as a glycol, glycol ether, lower alkyl alcohol (e. g. isopropanol), petroleum. distillates or even water, preferably in the presence of a soap, detergent or other emulsifying or wetting agent- The suspension of graphite particles, initially. present in the carrier in amounts between 20 and percent by weight, is diluted, then centrifuged or filtered, and the recovered crystals are suitably classified and incorporated into a suitable solvent lacquer or plastic which will produce the desired nacreous effect.

The graphite crystals 'of the present invention which produced the desired black,,lust rous nacreous effect are in the form of irregular opaque plates 1 to 50 microns a preferred averagesize of about 8 microns. This dimension is measured in the plane of the flat, plate-like crystal. The thicknessof such crystals would be of the order of about 0.1 to 1 micron.

Example A dispersion of finely divided graphite was prepared graphite of about 200 mesh size by milling the graphite in ethylene glycol monoethyl ether (Cellosolve) containing 1 percent sodiumlauryl sulfate The solids in the resulting slurry were separated therefrom by sedimentation and then again monoethyl ether to a solids This supsension was then centrifuged, theFlight-weight material remaining in the suspension being subsequently discarded. The solids resulting from the centrifugation had a pure black lustrous appearance and were of a plate-like configuration. The diameter of the particles was between about 1 and 50 microns, the average being 8 microns. The thickness :was from 0.1 to 1 micron.

The crystals produced by the procedure outlined in the: above example, when suspended in water. or inan organic solvent, "produce on stirring, the silky or pearly appearance which is typical of nacreous crystals. The motion of the liquid causes the crystals to be oriented luster isproduced as light is reflected from numerous crystal faces.

The form in which the nacreous graphite pigment is commonly prepared is that of a paste which contains as the vehicle thereof, a light-transmitting, preferably clear liquid which is compatible with lacquers, resins, and plastics. For certain applications it is desirable to use the nacreous pigment in the form of a dry powder, although drying often causes a partial loss in luster through agglomeration of individual crystal platelets. Other applications utilize the nacreous crystals in aqueous sussuitable composition for this purpose is:

.flw l of the pigments. General! a translucent or transparent plastic material such as cel ulose acetate, the alkyd resins, hsv n e n asw l as; e. y c. c d s r. resins. a foundto1be; quite useful. A typical paste composition useful for stock material, to be diluted" to a useful concentration levelis the following; 1 part (by weight) graphite 2 parts (by Weight) cellulose nitrate lacquer The lacquer may have a formulationsuch as the following:

midst any. clear acq er Percent llu n r i ss nd 8 Ethanol 3-20 Amyl acetate 89:

The water-washed crystals which have: been; described u a. st le. vehicle. or. e th r.

above can be made compatible" with a' lacquer-of; this type by being washed with a suitable water-miscible-organic solvent, such'as ethanol.

Whenused to make simulated pearlsby thecoating of alabaster'glass or plastic beads, the lacquer paste containing' one-third nacreous pigment is *further diluted with a clear cellulose nitrate lacquer of the appropriate viscosity. Such lacquers, suitable for coating objects by dipping, spraying, etc., for best resultsshould contain from 0.5 to 5 percent of-the graphitecrystals;

The solvent, instead of containing primarily amylacetate as indicated in the above example, may comprise buty-1- acetate, acetone; or other commonly used organic solvents.

For incorporation in aplastic, such as methylmethaerylate, it is convenient to disperse thenacreous' graphite in-apl'as'ticizer rather than in a-lacquer formulation. "A

. r Percent Nacreous graphiteg wm g 25.0 Acetone n}- 20.0 Dibutyl phthalate 55.0

centration of graphiteis 0.5 i053 percent of theweight of the casein.

The heat stability of the graphite also makes possible their use. as: nacreous pigments. in :transparentinorganic substances, such as glasses. The: dry crystals may be dispersed in molten glass,l.and then oriented by'the operationsutilized in molding orl blowingthe glass.

Inlall instances referred toabove the utilization of nacreous graphite produced a much more lustrous pure black pearly efiect than could beobtainedby dyeing white nacreouspigments.

'being'due to the lu he pregoingthe. inventionhas been described only in connection with preierred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein.

are obvious. Accordingly, it is preferred that this invention be bound not by, the specific disclosure herein, but only by the appending claims.

I claim:

1,. Anacreouspigrnent for producing alustrous black efiect, said effect being due to the presence therein of particles of finely-divided plate-like opaque, crystalline graphite, the. graphiteparticles being in the range of 1 to 50 microns in diameter'andj having a thickness not greater than 1 micron.

2. The pigment of claiml in ameter of the graphite particles is about 8 microns.

3. A nacreous composition having a pigment suspended therein-.forproducing a' lustrousblack effect, said effect being due to the presence in saidcomposition of particles offinel y-divided, plate-like, opaque, crystalline graphite, the graphite particlesbeing in the range of 1 to 50 microns in diameter and having a thickness not greater than 1 micron, the said graphite particles being suspended in a light-transmitting, liquid vehicle.

4. The composition of claim 3 in which the liquid vehicleis'a mixture of solvent and plasticizer.

5i A- nacreouscomposition having a pigment suspended thereinforproducing a lustrous, black eifect, said effect presence in said composition of particles offinely-divided, plate-like, opaque, crystalline graphite, the graphite particles beingin the range of 1 to 50 microns "in" diaineter and having a thickness of the order the said graphite'particles being susmicron,

'pend'ed'in-a light transinitting organic lacquer.

6: 'A nacreous" coating composition having a pigment suspended-therein-for producing a lustrous black effect, 'said eifect being; due to the presence in said composition of 0.5-to 5' percent of finely-divided, plate-like, opaque, crystalline graphite, the graphite particles being in the range of- 1'10 SOmicrons in diameter and having a thickness'of' the order of' Oil to 1 micron, the said graphite particles being suspended in a nitrocellulose lacquer.

' 7". A nacreous' plastic molded article having a pigment suspended therein for producing a lustrous black effect, said effect being due to the presence in said composition of 0.5" to 5 percent of finely-divided, plate-like, opaque, crystalline graphite, the graphite particles being in thefran'ge of 1 to 50 microns in diameter and having atthickness of the orderof 0.1 to 1 micron, the said graphite particles being suspended in a casein plastic.

8: The'composition' of claim 4 in which the solvent is acetone and the plasticizer is dibutyl phthalate.

Porter; News Edition (Am. Chem. Soc.) 19, Utility ofj=ColloidalGraphite, pp. 577-578 1941 which the average di- 

3. A NACREOUS COMPOSITION HAVING A PIGMENT SUSPENDED THEREIN FOR PRODUCING A LUSTROUS BLACK EFFECT, SAID EFFECT BEING DUE TO THE PRESENCE IN SAID COMPOSITION OF PARTICLES OF FINELY-DIVIDED, PLATE, OPAQUE, CRYSTALLINE GRAPHITE THE GRAPHITE PARTICLES BEING IN THE RANGE OF 1 TO 50 MICRONS IN DIAMETER AND HAVING A THICKNESS NOT GREATER THAN 1 MICRON, THE SAID GRAPHITE PARTICLES BEING SUSPENDED IN A LIGHT-TRANSMITTING, LIQUID VEHICLE. 